Synthesis, anticancer activities and molecular modeling studies of novel indole retinoid derivatives

Research status of indole-modified natural products

Indole is a heterocyclic compound formed by the fusion of a benzene ring and pyrrole ring, which has rich biological activity. Many indole-containing compounds have been sold on the market due to their excellent pharmacological activity. For example, vincristine and reserpine have been widely used in clinical practice. The diverse structures and biological activities of natural products provide abundant resources for the development of new drugs. Therefore, this review classifies natural products by structure, and summarizes the research progress of indole-containing natural product derivatives, their biological activities, structure-activity relationship and research mechanism which has been studied in the past 13 years, so as to provide a basis for the development of new drug development.

Discovery of novel RARα agonists using pharmacophore-based virtual screening, molecular docking, and molecular dynamics simulation studies

Nuclear retinoic acid receptors (RARs) are ligand-dependent transcription factors involved in various biological processes, such as embryogenesis, cell proliferation, differentiation, reproduction, and apoptosis. These receptors are regulated by retinoids, i.e., retinoic acid (RA) and its analogs, as receptor agonists. RAR agonists are promising therapeutic agents for the treatment of serious dermatological disorders, including some malignant conditions. By inducing apoptosis, they are able to inhibit the proliferation of diverse cancer cell lines. Also, RAR agonists have recently been identified as therapeutic options for some neurodegenerative diseases. These features make retinoids very attractive molecules for medical purposes. Synthetic selective RAR agonists have several advantages over endogenous ones, but they suffer poor pharmacokinetic properties. These compounds are normally lipophilic acids with unfavorable drug-like features such as poor oral bioavailability. Recently, highly selective, potent, and less toxic RAR agonists with proper lipophilicity, thus, good oral bioavailability have been developed for some therapeutic applications. In the present study, ligand and structure-based virtual screening technique was exploited to introduce some novel RARα agonists. Pharmacokinetic assessment was also performed in silico to suggest those compounds which have optimized drug-like features. Finally, two compounds with the best in silico pharmacological features are proposed as lead molecules for future development of RARα agonists.

Novel indole retinoid derivative induces apoptosis and cell cycle arrest and modulates AKT and ERK signaling in HL-60 cells

Chemotherapy with targeted drugs is the first line therapy option for acute and chronic myeloid leukemia. However, hematopoietic stem cell transplantation may be used in high-risk patients or patients with failed responses to chemo drugs. Discovery and development of more effective new agents with lower side effects is the main aim of leukemia treatment. In this study, a novel retinoid compound with tetrahydronaphthalene ring was synthesized and evaluated for anticancer activity in human chronic and acute myeloid leukemia cell lines K562 and HL-60. Novel N-(1H-indol-1-yl)-5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalene-2-carboxamide was synthesized based on molecular hybridization of the two different bioactive structures retinoid head and indole. The effects of the synthesized carboxamide compound, which was referred to as compound 5, were determined in K562 chronic myeloid leukemia and HL-60 acute myeloid leukemia cell lines and L929 fibroblast cell line, which served as a control. Colorimetric MTT and caspase3 activity tests, flow cytometry, western blot, and microscopic examinations were used to evaluate biological activity. Compound 5 more effectively induced cell death in HL60 cells in comparison to K562 cells and L929 fibroblast cells. Therefore, further mechanism of cell death was investigated in HL60 cell line. It was found that compound 5 induced remarkable cytotoxicity, caspase3 activation, and PARP fragmentation in HL60 cells. Flow cytometric staining showed that the percentage of cells arrested in G0/G1 was also increased with compound 5 treatment. Important modulator proteins of cell proliferation p-ERK, p-AKT, and p-m-TOR were also found to be inhibited with compound 5 treatment. Collectively, our results reveal compound 5, which is a novel indole retinoid compound as a potential active agent for the treatment of acute promyelocytic leukemia.

Atroposelective Construction of Nine-Membered Carbonate-Bridged Biaryls

We herein demonstrated an efficient method for the atroposelective construction of nine-membered carbonate-bridged biaryls through vinylidene ortho-quinone methide (VQM) intermediates. Diverse products with desirable pharmacological features were synthesized in satisfying yields and good to excellent enantioselectivities. In subsequent bioassays, several agents showed considerable antiproliferative activity via the mitochondrial-related apoptosis mechanism. Further transformations produced more structural diversity and may inspire new ideas for developing functional molecules.

A brief review of the biological potential of indole derivatives

Background

Various bioactive aromatic compounds containing the indole nucleus showed clinical and biological applications. Indole scaffold has been found in many of the important synthetic drug molecules which gave a valuable idea for treatment and binds with high affinity to the multiple receptors helpful in developing new useful derivatives.

Main text

Indole derivatives possess various biological activities, i.e., antiviral, anti-inflammatory, anticancer, anti-HIV, antioxidant, antimicrobial, antitubercular, antidiabetic, antimalarial, anticholinesterase activities, etc. which created interest among researchers to synthesize a variety of indole derivatives.

Conclusion

From the literature, it is revealed that indole derivatives have diverse biological activities and also have an immeasurable potential to be explored for newer therapeutic possibilities.

Enantioselective Dehydrative γ-Arylation of α-Indolyl Propargylic Alcohols with Phenols: Access to Chiral Tetrasubstituted Allenes and Naphthopyrans

Herein, we report an enantioselective dehydrative γ-arylation of α-indolyl propargylic alcohols with phenols via organocatalysis, which provides efficient access to chiral tetrasubstituted allenes and naphthopyrans in high yields with excellent regio- and enantioselectivities under mild conditions. This method features the use of cheaply available naphthols/phenols as the C-H aryl source and liberating water as the sole byproduct. Control experiments suggest that the excellent enantioselectivity and remote regioselectivity stem from dual hydrogen-bonding interaction with the chiral phosphoric acid catalyst.

Synthesis of Indolyl Pyrazole Scaffolds as Potential Anti-cancer Agents and their Molecular Modelling Studies

Background::

Indole and pyrazoles are one of the prime structural units in the field of medicinal chemistry and have been reported to exhibit a variety of biological activities specifically anti-cancer. In view of their medicinal significance, we synthesized a conjugate of the two moieties to get access to newer and potential anti-cancer agents.

Methods:

Indolyl pyrazoles [3-(1,3-diphenyl-1H-pyrazol-4-yl)-2-(1-methyl-1H-indole-3-carbon yl)acrylonitriles] (4a-l) were synthesized by adopting simple and greener protocol and all the synthesized derivatives were docked against Bcl-2 protein and the selected chemical moieties were screened for their cytotoxicity by using the MTT assay.

Results: :

All the synthesized compounds were docked against BCL-2 protein in order to understand their binding pattern. Among the 12 compounds docked, 4d, 4f, 4h, 4j, and 4l compounds exhibited better protein binding interactions and the same were screened for their anti-cancer activity against A549 (lung) cancer cell lines at a concentration of 100 μM using Doxorubicin as standard. Substitutions such as N-benzyl, N-ethyl groups and halogen groups such as Br, Cl on indole ring showed moderate activity against A-549 cell lines.

Conclusion::

Among the 5 indolyl pyrazole derivatives screened, compounds 4h and 4j showed significantly better activity with an IC50 of 33.12 and 34.24 μM, respectively. Further, structural tweaking of the synthesized new chemical entities may lead to potential hit/lead-like molecules.

New Thiazoline-Tetralin Derivatives and Biological Activity Evaluation

In this study, novel N′-(3-cyclohexyl/phenyl-4-(substituted phenyl)thiazole-2(3H)-ylidene)-2-[(5,6,7,8-tetrahydronaphthalen-2-yl)oxy]acetohydrazide (4a–4k) derivatives were synthesized and their anticancer potency were evaluated on human breast adenocarcinoma cell line (MCF-7), human lung carcinoma cell line (A549) and mouse embryoblast cell line (NIH/3T3) using the MTT method, DNA synthesis inhibition and flow cytometric analysis. Compound 4e bearing 4-methoxyphenyl moiety exhibited the highest antitumor efficiency against MCF-7 cell line with higher DNA synthesis inhibition and apoptotic cell percentages (ealy+late apoptotic cell). On the other hand, compounds 4f, 4g, and 4h bearing 4-bromo, 4-chloro and 4-florophenyl moieties, respectively caused excellent apoptosis levels against A549 cell line when treated with lower concentration even than cisplatin. Anticholinesterase activity of the compounds were also tested, compound 4h showed 49.92% inhibition of acetylcholinesterase (AChE).

Structure-activity relationship (SAR) study and design strategies of nitrogen-containing heterocyclic moieties for their anticancer activities

The present review article offers a detailed account of the design strategies employed for the synthesis of nitrogen-containing anticancer agents. The results of different studies describe the N-heterocyclic ring system is a core structure in many synthetic compounds exhibiting a broad range of biological activities. Benzimidazole, benzothiazole, indole, acridine, oxadiazole, imidazole, isoxazole, pyrazole, triazoles, quinolines and quinazolines including others drugs containing pyridazine, pyridine and pyrimidines are covered. The following studies of these compounds suggested that these compounds showed their antitumor activities through multiple mechanisms including inhibiting protein kinase (CDK, MK-2, PLK1, kinesin-like protein Eg5 and IKK), topoisomerase I and II, microtubule inhibition, and many others. Our concise representation exploits the design and anticancer potency of these compounds. The direct comparison of anticancer activities with the standard enables a systematic analysis of the structure-activity relationship among the series.

N′-((2-(6-bromo-2-oxo-2H-chromen-3-yl)-1H-indol-3-yl)methylene)benzohydrazide as a probable Bcl-2/Bcl-xL inhibitor with apoptotic and anti-metastatic potential

A wide number of marketed drugs and drug candidates in cancer clinical development contain halogen substituents. The aim of the present study was to synthesize a series of halogen incorporated indole-coumarin hybrid schiff bases - N'-((2-(2-oxo-2H-chromen-3-yl)-1H-indol-3-yl)methylene)benzohydrazides and to investigate their apoptotic and anti-migratory potential in human breast adenocarcinoma cells as well as to examine their Bcl-2 and Bcl-xL protein binding ability via in silico docking. Hybrid 5g with a bromine atom in position-7 of coumarin ring displayed significant dose dependent cytotoxic activity with high selectivity to MCF-7 cells in MTT assay. Cell cycle progression analysis of 5g treated cells using flow cytometer exhibited a cell cycle arrest in the S phase and accumulation of cells in the subG1 phase. The apoptotic mode of cell death induced by 5g was further confirmed by Annexin-V staining assay. The wound healing assay revealed a profound impairment in the migration of MCF-7 cells presumably due to down-regulation of Bcl-2 and Bcl-xL proteins induced by 5g as observed in immunoblotting analysis. SAR studies of these hybrid molecules based on cell viability and docking were also probed. The most active pharmacophore 5g was found to bind favourably to Bcl-2 and Bcl-xL in docking simulation analysis suggesting it to be a probable small molecule Bcl-2/Bcl-xL inhibitor and a potential lead for breast cancer chemotherapy with apoptotic and anti-metastatic properties.

Retinoic acid signaling pathways in development and diseases

Retinoids comprise a group of compounds each composed of three basic parts: a trimethylated cyclohexene ring that is a bulky hydrophobic group, a conjugated tetraene side chain that functions as a linker unit, and a polar carbon-oxygen functional group. Biochemical conversion of carotenoid or other retinoids to retinoic acid (RA) is essential for normal regulation of a wide range of biological processes including development, differentiation, proliferation, and apoptosis. Retinoids regulate various physiological outputs by binding to nuclear receptors called retinoic acid receptors (RARs) and retinoid X receptors (RXRs), which themselves are DNA-binding transcriptional regulators. The functional response of RA and their receptors are modulated by a host of coactivators and corepressors. Retinoids are essential in the development and function of several organ systems; however, deregulated retinoid signaling can contribute to serious diseases. Several natural and synthetic retinoids are in clinical use or undergoing trials for treating specific diseases including cancer. In this review, we provide a broad overview on the importance of retinoids in development and various diseases, highlighting various retinoids in the drug discovery process, ranging all the way from retinoid chemistry to clinical uses and imaging.